In my U.S. Pat. No. 5,090,467, issued on Feb. 5, 1992, and entitled "Vertical Blind Track Protector", I described a new and improved vertical blind construction that automatically placed the vanes into their correct open position whenever a user desired to traverse the blind. As there set forth, if a user attempted to traverse the blind in the "vane closed" position, my described arrangement automatically rotated the vanes to the "vane open" position before the unit traversed. The track protector there shown thus operated to prevent the vanes of the blind from traversing in the closed position, and causing damage.
While the solution depicted in my U.S. Pat. No. 5,090,467 overcame one of the problems confronting the vertical blind industry, another problem continued to exist--that of "bounceback", or a refusal of the vanes to remain in a tightly closed position once so oriented by a user. As those involved in the art recognize, vanes (or louvers) have a tendency to open slightly by themselves--as when vertical blinds are hung over open windows or sliding doors, due to puffs of breeze, or accidentally jostling into them. Investigation has also shown that one cause for this can also be traced to the use of slightly twisted pinion rods in the track, or a twisting of the channel when installed on an uneven surface.
Analysis, furthermore, has shown that the smooth, direct rack and pinion-planetary gear rotation mechanism commonly employed in many modern vertical blind tracks also contributes to this "bounceback" problem. Typical to this are those arrangements described in U.S. Pat. Nos. 4,657,060 and 4,834,163--which utilize relatively high speed reducing drives which are very convenient to use but which are very susceptible to this problem. In fact, their conveniences have led to an increase in the popularity of vertical blinds with architects and consumers alike, who balance that out with their dislikes of the vane-opening problem.
Some manufacturers have attempted to avoid this "bounceback" by designing the drive and rotating mechanisms deliberately to have more friction on the planetary gears employed. For example, some accomplish that by allowing the gears to rub against the inside wall of the housing, while others include a restricting device consisting of a flat plate which increases the resistance of the gears. While such approaches make for tighter, more secure vane closure, they all require an increased force be applied in order to effect the rotation. Such harder "action" is quite noticeable, and many times disapproved--most frequently by users of large tracks with heavy load. Such approaches, additionally, have been observed to be too stiff in their operations to allow the vanes to completely return to the open position when traversed (to utilize the advantages of my vertical blind track protecting system), resulting in an increased drag on the traverse "action", and increase stress on the various components of the vertical track system.
A different type of approach to the problem is present in U.S. Pat. No. 4,122,884, which employs a worm and screw gear to transfer rotational forces from a pull-chain to the pinion rod. While the approach allows for very precise louver rotation and fairly tight closure, there is a definite lack of smoothness as is associated with the preferable planetary gear constructions, and introduces other problems of its own. For example, the automatic rotation of my U.S. Pat. No. 5,090,467 cannot be utilized because the worm gear is unable to work in reverse direction. That is, while the louver chain can rotate the worm gear to turn the pinion and suspended vanes, any attempt to turn the pinion directly or by means of traverse cord action on my track protector does not budge the gears.
Yet another approach of obtaining vertical blind vane control locking is set forth in U.S. Pat. No. 5,163,492. There, a device fastens to a wall surface near the actuating chain, and is so designed that beads on the chain can be engaged manually into locking slots in the device to prevent movement of the vanes. One disadvantage of such arrangement will be noted to be that the auto-rotation method patented by me cannot be utilized with the lock deployed in any position--attempts to traverse the blind when the vanes are in the locked closed position virtually guarantees track damage. Secondly, proper operation requires instruction in carrying out the procedure, and while fairly simple, any manual locking and unlocking of the chain is an inconvenient step. Thirdly, experience has shown that installers dislike doing anything more than they have to, and the teachings of this patent require that there be extra work for the installation. (This, along with the cost of the mounting hardware, adds to the price charged to the consumer.) Additionally, incorrect and/or inadequate installation of the lock has been found to result in damage to the lock, to the wall on which it is mounted, to the vertical blind track, and to the brackets supporting the track. Even when correctly installed, another disadvantage of this configuration is that the job still requires mounting holes to be drilled into a wall, molding, or jamb--which is objectionable to the user in many instances.